The cost of species gone 'missing'

A resilient ecosystem can better withstand global warming and will deliver what humans need, whether it's abundant tuna from the seas or fresh water tumbling down a mountainside.

from the June 21, 2007 edition

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Resplendent quetzals, iridescent tropical birds that he used to observe feeding frogs to their young, are scarcer. Quetzal hatchlings may have lost a vital source of protein and calcium with the disappearance of once-abundant amphibians, he reasons. Keel-billed toucans, meanwhile, have moved up from the foothills to the mountain, perhaps competing with the quetzal. So has the morpho, a bright blue lowland butterfly. Snakes, which also fed on the frogs, are much harder to come by even as lowland honeybees that previously avoided the mountain's hive-infesting fungi now swarm up the mountain.

"We lived in cloud forest when we first arrived," Mr. Fogden says. "It's not cloud forest anymore, really."

Besides losing potential ingredients for new drugs or other useful compounds, scientists worry about more lost benefits as species vanish. Healthy ecosystems are complex. Complexity lends resilience, the ability to ride out disturbances. A resilient ecosystem will continue delivering the "services" humans expect, whether it's harvesting abundant tuna from the sea or tapping fresh water as it tumbles down a mountainside. Each species removed from an ecosystem brings it closer to a largely invisible threshold of collapse.

Scientists tend to use this economic reasoning about nature's importance when talking with journalists. When pressed, though, they make a different argument.

Species "should be preserved because of their intrinsic value," says Kayri Havens, director of the Institute for Plant Biology and Conservation at the Chicago Botanic Garden, "because they deserve to exist. Just as we do."

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